1. Field of the Invention
The present invention relates to a numerical control device, and in particular, relates to a numerical control device having a tool correction function in skiving processing.
2. Description of the Related Art
In skiving processing with a turning machine, the processing is performed with the Z-axis and the Y-axis being moved using a tool having a straight blade which is disposed obliquely with respect to the rotational axis line of a workpiece in the YZ-plane (see Japanese Patent No. 3984052).
In the case of a tool illustrated in FIG. 10A, the straight blade of the tool is needed to be attached parallel to the rotational axis line (Z-axis line) in the ZX-plane as in FIG. 10B in order to perform processing precisely into a desired shape in this processing. If the tool is not attached parallel thereto as in FIG. 10C, the diameter of the processed article is not constant between the cutting start position and the cutting end position. In such a case, the processed article is needed to be measured once after the cutting, and based on the result, the processing program is needed to be modified, which lays a burden on an operator.
When the straight blade of the tool is parallel to the rotational axis line (Z-axis line) in the ZX-plane, as illustrated in FIG. 11, the cutting amount is constant regardless of the position of the tool even in turning with the Z-axis and the Y-axis being moved.
On the contrary, a case will be considered where the straight blade of the tool is not parallel to the rotational axis line (Z-axis line) in the ZX-plane as illustrated in FIG. 12. When the straight blade of the tool inclines toward the rotational axis line side with respect to the progress direction, the cutting amount is increased and the cutting load is increased as the tool is moving, which causes precision in the processing surface to suffer dispersion. Moreover, the diameter of the processed article varies between the start position and the end position of cutting.